Motor Controllers
Installation & Setup Guide
How to mount and wire the SP-3P-SD complete three-phase star-delta smart motor starter.
Section: Starter 3-Phase Star-Delta
Safety Requirements
The SP-3P-SD handles 415V AC three-phase mains on its input terminals and operates three contactors internally. All wiring must be performed with the mains isolated, locked off, and proved dead at all three phases. This is a high-power assembly — only qualified electricians should perform the mains and motor wiring.
Steps
- Isolate the three-phase supply at the main switch-disconnector or incomer MCB. Lock out and tag out before opening the enclosure.
- Prove dead at R, S, T supply terminals and at the motor terminals U1, V1, W1, U2, V2, W2 using a calibrated voltage tester before touching any wiring.
- Star-delta starters handle high starting current even with reduced-voltage starting — all mains connections must be torqued to the specification on the terminal label.
- Never short-circuit U1–V1–W1 and U2–V2–W2 together at the motor terminal box — this bypasses the star-delta wiring and causes a short circuit when the star contactor closes.
- The MX-3P-SD module sequencing controls the three contactor coils — never manually close the star and delta contactors simultaneously. This is prevented by interlocking in the SP-3P-SD assembly.
Tools Required
Tool Checklist
| Preview | Quantity | Item | Details |
|---|---|---|---|
| × 1 | Flat-Head Screwdriver (6 mm) | For R/S/T input and U1/V1/W1/U2/V2/W2 mains terminal screws | |
| × 1 | Flat-Head Screwdriver (3 mm) | For MX-3P-SD RS485 and 12V DC terminal screws | |
| × 1 | Torque Screwdriver | For torquing high-current mains terminals to the rated Nm — critical for connections above 32A | |
| × 1 | Wire Strippers | For preparing motor and supply cable ends (4 mm² to 16 mm² depending on motor rating) | |
| × 1 | Calibrated Voltage Tester | To prove dead at all six motor terminals and three supply phases before wiring | |
| × 1 | Clamp Meter | To measure motor running current on all three phases during commissioning | |
| As required | RS485 Shielded Twisted-Pair | 1.0 mm² shielded cable from MX-3P-SD RS485 terminals to gateway |
Flat-Head Screwdriver (6 mm)
For R/S/T input and U1/V1/W1/U2/V2/W2 mains terminal screws
Flat-Head Screwdriver (3 mm)
For MX-3P-SD RS485 and 12V DC terminal screws
Torque Screwdriver
For torquing high-current mains terminals to the rated Nm — critical for connections above 32A
Wire Strippers
For preparing motor and supply cable ends (4 mm² to 16 mm² depending on motor rating)
Calibrated Voltage Tester
To prove dead at all six motor terminals and three supply phases before wiring
Clamp Meter
To measure motor running current on all three phases during commissioning
RS485 Shielded Twisted-Pair
1.0 mm² shielded cable from MX-3P-SD RS485 terminals to gateway
What's in the Box
Included Items
| Preview | Quantity | Item | Details |
|---|---|---|---|
| × 1 | SP-3P-SD Assembly | Pre-assembled main + star + delta contactors + overload relay + MX-3P-SD module | |
| × 1 | RS485 Terminal Block | 2-position terminal for RS485 A and B wiring to gateway | |
| × 1 | 12V DC Input Terminal | 2-position terminal for 12V DC control power supply | |
| × 1 | Phase Sense Terminal Block | 3-position terminal for R, S, T phase sense wires | |
| × 1 | Panel Mounting Bracket | Back-plate bolt-on bracket for SP-3P-SD-32 and SP-3P-SD-65 models | |
| × 1 | Motor Terminal Wiring Diagram | Printed 6-terminal star-delta motor wiring diagram for the SP-3P-SD | |
| × 1 | Quick Installation Card | Terminal reference card — supply R/S/T, motor U1/V1/W1/U2/V2/W2, RS485, 12V DC |
SP-3P-SD Assembly
Pre-assembled main + star + delta contactors + overload relay + MX-3P-SD module
RS485 Terminal Block
2-position terminal for RS485 A and B wiring to gateway
12V DC Input Terminal
2-position terminal for 12V DC control power supply
Phase Sense Terminal Block
3-position terminal for R, S, T phase sense wires
Panel Mounting Bracket
Back-plate bolt-on bracket for SP-3P-SD-32 and SP-3P-SD-65 models
Motor Terminal Wiring Diagram
Printed 6-terminal star-delta motor wiring diagram for the SP-3P-SD
Quick Installation Card
Terminal reference card — supply R/S/T, motor U1/V1/W1/U2/V2/W2, RS485, 12V DC
Removing an Old Starter
When upgrading from an older star-delta starter, the SP-3P-SD replaces the complete starter assembly. Existing main, star, and delta contactors and their timer logic should be removed or fully isolated before the new unit is commissioned.
Steps
- Remove the old star-delta timer, interlock wiring, and contactor coil control wiring from service before connecting the SP-3P-SD.
- Do not reuse internal old contactor interlocks, because the SP-3P-SD already includes its own coordinated star-delta control sequence.
- Reuse the six motor leads only after confirming insulation, identification, and termination quality at both the motor and panel ends.
- If the previous starter used a different terminal naming convention, relabel the motor conductors clearly as U1, V1, W1, U2, V2, W2 before reconnection.
- After replacement, verify that no old timer or auxiliary contact path can energise the star or delta contactor independently of the SP-3P-SD.
Guided Help Center
Identify the old star-delta contactors, timer, and interlock wiring to be removed from service.
Assembly Mounting
The SP-3P-SD assembly contains three contactors and is physically larger than the SP-3P (DOL) assembly. All models mount on the enclosure back plate using the supplied bracket — DIN rail is not recommended for the star-delta assembly due to its weight and vibration during switching.
Steps
- With mains isolated and proved dead, bolt the SP-3P-SD assembly to the enclosure back plate using M4 bolts through the supplied bracket.
- Leave at least 50 mm clearance on each side and above/below for heat dissipation and ventilation — three contactors generate significant heat under repeated starting.
- Mount the 12V DC DIN rail power supply separately on a DIN rail section in the enclosure.
- Plan cable routes for: R/S/T supply cables (from switch-disconnector); six motor cables (U1, V1, W1, U2, V2, W2 from motor terminal box); RS485 cable to gateway. Route motor and supply cables in separate ducts from the RS485 and 12V DC wiring.
Guided Help Center
Choose a rigid back-plate location with enough space for the larger star-delta assembly.
Supply & Motor Terminal Wiring
The SP-3P-SD has six motor terminals (U1, V1, W1, U2, V2, W2) and three supply input terminals (R, S, T). The internal star and delta contactor connections are pre-wired inside the assembly — do not attempt to rewire the internal contactor connections.
Steps
- Connect three-phase supply: R → SP-3P-SD terminal R; S → terminal S; T → terminal T.
- At the motor terminal box, remove all internal links or shorting bars. The SP-3P-SD requires six separate motor terminals — the star and delta connections are made inside the SP-3P-SD assembly.
- Connect motor terminal U1 to SP-3P-SD motor terminal U1.
- Connect motor terminal V1 to SP-3P-SD motor terminal V1.
- Connect motor terminal W1 to SP-3P-SD motor terminal W1.
- Connect motor terminal U2 to SP-3P-SD motor terminal U2.
- Connect motor terminal V2 to SP-3P-SD motor terminal V2.
- Connect motor terminal W2 to SP-3P-SD motor terminal W2.
- Connect the motor earth (PE) to the enclosure earth bar — not through the SP-3P-SD assembly.
- Set the overload relay FLA dial to the motor nameplate delta current (the full-load current at 415V in delta configuration — same as the nameplate FLA for standard motor nameplates).
- Connect R, S, T phase sense wires (thin 1.0 mm² wire) from the supply input terminals to the MX-3P-SD phase sense terminals R, S, T.
- Connect 12V DC V+ and V− to the MX-3P-SD control power terminals.
- Connect RS485: A core → RS485-A; B core → RS485-B. Shield to panel earth.
Guided Help Center
Connect the three incoming supply phases to R, S, and T on the SP-3P-SD.
Commissioning & First Start
Steps
- Restore 12V DC power first — confirm the MX-3P-SD LED illuminates (green or blue).
- Restore three-phase mains supply to the panel.
- Complete Gateway Linking — see the Gateway Linking guide — and configure the star-delta transition timer before the first start.
- Set the star-delta transition timer in the app: Device Settings → Motor → Star-Delta Timer. Start with 8 seconds for motors up to 22 kW; increase to 12–15 seconds for larger motors.
- From the app, tap Manual Control → Start. The sequence: main contactor clicks (mains connected), star contactor clicks (star configuration), star timer runs, star contactor releases, delta contactor clicks (delta configuration).
- Measure motor current at startup with a clamp meter: confirm the star-phase current is significantly lower than DOL starting current, then rises to delta running current after transition.
- If transition fails (stays in star): see Troubleshooting — Star-Delta Transition Failure.
- Confirm all three phases read balanced current in delta running mode.